Device for liquid development

ABSTRACT

A liquid type developing device for an electrophotographic reproduction machine, wherein a temporary storing section or sump is provided contiguous to a developing agent well-up means to regulate flow rate of the developing agent to be fed to a developing electrode facing the outer peripheral surface of a photosensitive drum, on which an electrostatic latent image to be developed is formed, thereby avoiding undesirable disturbances to the developed image owing to the flow of the developing agent at an excessively high speed.

i United States Patent Yamada et al. [45] Nov. 4, 1975 [5 DEVICE FOR LIQUID DEVELOPMENT 3,664,298 5/1972 Giaimo, Jr. 118/637 3,752,119 8/1973 Matkan 118/637 [75] Inventors Katuhlko Yamada Yokohama 3,753,174 8/1973 Miller 118/010. 23 E Takada, Kawasakl, both of 3,802,388 4/1974 La Poma 118/010. 23

apan 73 Assignee: Canon Kabushiki Kaisha, Tokyo, Primary ExaminerMervin Stein Japan Assistant Examiner-Douglas Salser Attorney, Agent, or Firm-Fitzpatrick, Cella, Harper [22] Filed. May 6, 1974 & Scimo 21 Appl. No.: 467,483

[57] ABSTRACT [30] F i A li ti P i i D A liquid type developing device for an electrophoto- May H 1973 Japan 4852381 graphic reproduction machine, wherein a temporary storing section or sump is provided contiguous to a de- 52 US. 01 118/637- 118/010 23 doping agent well'up means to regulate flow of [51] Int. G03; 15/10 the developing agent to be fed to a developing elec- [58] Field 61 118/010. 23 637- facing Outer Peripheral Surface Of a Photo- 117 37 LE; 355 427 sens1t1ve drum, on which an electrostatic latent image 1 to be developed is formed, thereby avoiding undesir- [56] References Cited able disturbances to the developed image owing to the flow of the developing agent at an excessively high UNITED STATES PATENTS speed 3,263,649 8/1966 Heyl et al. ll8/637 3,651,782 3/1972 MacDonald, Jr. 118/637 4 Clams, 3 Drawmg Figures U.S. Patent Nov. 4, 1975 Sheet 1 of 3 3,916,829

U.S. Patent Nov. 4, 1975 FIG. 2

Sheet 2 of 3 3,916,829

FIG. 5

U.S. Patent Nov. 4, 1975 Sheet 3 of3 3,916,829

DEVICE FOR LIQUID DEVELOPMENT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a developing device to cause an electrostatic latent image formed on a photosensitive image holding means by the electrophotographic method to be developed thereon. More particularly, the invention is concerned with such developing device using a liquid developing agent or developer.

2. Description of the Prior Art In the development of the electrophotograph, it is indispensable that an electrode for development be made as close as possible to the face of a latent image, and, at the same time. a sufficient amount of the developing agent be fed in the gap between the electrodes and the latent image in order for a toner to be adhered onto the latent image surface as faithfully as possible in accordance with distribution of the electric charge of such electrostatic latent image.

In the case of the development in a liquid developer, a toner for exposing the electrostatic latent image to view is applied onto the surface of a photosensitive q body by way of a liquid as a carrier with the consequence that there take place various defects such as the so-called flow of the image, in which the developed image leaves trails on the surface of the photosensitive body due to a large flow rate of the developing agent through the gap between the latent image surface and the developing electrode, unevenness in the developed image which makes it difficult to obtain a steadily developed, visible image due to non-uniform flow of the developing agent, and others.

SUMMARY OF THE INVENTION In view of the above-described various defects inherent in the conventional liquid type developing device, it is an object of the present invention to provide a liquid type developing device of an improved construction.

It is another object of the present invention to provide a liquid type developing device, in which the flow rate of a developing liquid to be fed to the latent image surface is regulated arbitratily so as to enable a good image free from any irregularity in development to be reproduced constantly.

it is still another object of the present invention to provide a liquid type developing device of a simplified construction which is capable of regulating the flow rate of the developing liquid to a required degree.

According to the present invention as summarized in the preceding, the flow rate of the developing agent to be fed from a liquid reservoir is regulated at the time of developing the electrostatic latent image formed on an image holding member so that sufficient amount of the developing agent may be fed on and contacted with the surface of the image holding member, whereby the image-development in large capacity with a small size of the device can be realized without lowering the quality of the developed image.

The foregoing objects of the present invention as well as the construction and'function of the present device will become more apparent from the following detailed description thereof when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a cross-sectional view showing the main part of an electrophotographic reproduction machine in the vicinity of a photosensitivedrum equipped with the developing device according to the present invention;

FIG. 2 is a front view of the electrophotographic reproduction machine shown in FIG. I;

FIG. 3 is a perspective view of an electrode for the development;

FIG. 4 is a cross-sectional view of the developing electrode shown in FIG. 3) taken along the line IV-IV;

FIG. 5 is a side elevational view partly in longitudinal cross-section of the developing electrode shown in FIG. 3;

FIG. 6 is another embodiment of the present invention; and

FIGS. '7 and 8 are, respectively, further embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION As mentioned above. FIGS, I and 2 indicate, respectively, a cross-sectional view and a front view of an electrophotographic reproduction machine for use in the present invention, the reproduction machine being of a type utilizing the electrophotographic method in accordance with the socalled NP Process.

The electrophotographic reproduction machine of the type shown in the drawing is constructed with a photosensitive drum I composed of a photo-sensitive layer and a transparent insulative layer covering the photo-sensitive layer, which rotates in the clockwise direction; a primary charger 2 provided at one place around the photo-sensitive drum I; discharger 3 provided adjacent to the primary charger 2; a lamp 4 for light exposure; a developing device 5 disposed beneath the photo-sensitive drum 1, and comprising a vessel 7 to contain developing liquid 6, a developing electrode 8, a pair of springs to push the developing electrode 8 foward the outer periphery of the photo-sensitive drum I through a spacer or other interposing means leaving a very small gap or clearance therebetween, a pump P operated by a motor M to agitate the developing agent and pump it up to the electrode; a postcharger It); an image transfer means II to transfer a developed, visible image onto a printing paper PP fed from a paper feeding source; a separating means I2 to separate the paper onto which the image has been transferred; and a blade cleaner I3 press-contacted on the outer peripheral surface of the photosensitive drum I to remove the developing liquid remaining thereon.

In the electrophotographic reproduction machine of the above-described construction, the photo-sensitive drum I is first charged in positive polarity by the primary charger 2, after which, when the charged portion of the drum; I reaches the exposing section consisting of the discharger 3 and the exposure lamp 4, it undergoes a slit-exposure to receive a master image thereon, and, simultaneously, it is subjected to ac. discharge or do secondary charge of an opposite polarity. In the subsequent total exposure to be carried out by the lamp 4, an electrostatic latent image is formed on the surface of the photosensitive drum I followed by entering into the developing device 5 where the electrostatic latent image on the photosensitive drum I is developed by a toner contained in the developing liquid which has been pumped up by the pump P to the position of the developing electrode S to be turned into a visible image. The thus developed, visible image is then charged by the post-charger to squeeze excess amount of the developing liquid on the photosensitive drum 1 without disturbing the developed image. Thereafter, the image is transferred onto the printing paper PP which has been fed from the paper feeding source to the image transfer means 11, and thus image-transferred paper is separated from the drum 1 by the separating means 12 to be led to a drying and fixing section (not shown). After the image-forming, developing, and transferring operation, the residual toner and developing liquid on the photosensitive drum 1 is wiped off by the blade cleaner 13 press-contacted onto the outer peripheral surface of the drum 1, and the second cycle onward of the operation is repeated.

It is of course possible that the developing device according to the present invention can be used not only for the above-mentioned type of the electrophotographic reproduction machine, but also for any other type of the reproduction machine, to which the electrophotographic printing process is applied.

In the following, the structure of the developing device according to the present invention will be described in more detail.

Referring to FIGS. 3, 4 and 5 which are a perspective view, a cross-sectional view, and a side elevational view, respectively, of the developing part of the device according to the present invention, the developing device is constructed with electrodes 8, a flow path 8a for the developing liquid, a well-up groove 8b of the developing liquid, a plurality of the feeding ports 8c for the developing liquid formed in one longitudinal side wall of the developing electrode 8, i.e., along the ridge line of the photosensitive drum 1, a developing liquid feeding tube 14 to feed the developing liquid to the electrode by means of the feeding pump P, a developing liquid storing sump 15, and developing liquid stopping plates 16 at both ends of the electrode.

The conventional developing device is of such construction that the developing liquid fed from the feeding pump passes through the developing liquid feeding tube 14 and pours forth directly from the well-up groove 8b of the developing electrode 8, hence the state of Welling-up of the liquid differs at the place where the developing liquid feeding tube is provided and at the other places with the consequent nonuniformity in the overall flow of the developing liquid and irregularities in the image formed on the photosensitive drum 1.

However, when the developing device is so constructed as shown in FIGS, 3, 4 and 5 that the developing liquid fed from the developing liquid feeding tube 14 is once filled in the liquid storing sump 15, is then caused to flow into the liquid flow path 8a below the liquid well-up groove 8b through the plurality of the liquid feeding ports 8c formed in the side wall of the liquid flow path 8a along the ridge line direction of the photosensitive drum 1, i.e., in the longitudinal direction of the developing electrode, and is finally intercepted by the liquid stopping plates 16 provided at and covering both ends of the liquid flow path 8a and the liquid wellup groove 8b, and is caused to well up from the groove 8/) to the surface of the latent image on the photosensitive drum 1, it becomes possible to secure uniform Welling-up of the developing liquid toward the photosensitive drum 1 so as to eliminate unevenness or irregularity in the development. In addition, by designing the well-up groove in the form of a slit, smooth and satisfactory Welling-up of the developing liquid is made possible.

In another embodiment of the present invention as shown in FIG. 6, the well-up groove 8b is disposed at a position opposite the rotational direction of the photo sensitive drum 1 by a degree from the intersection of the developing electrode and the vertical plane including the center of the drum, and the slit-opening of the well-up groove 8b is tilted by ,8 degree with respect to a line connecting the center of the drum 1 and the center of the slit-opening in the rotational direction of the drum. In so doing, the developing time after the welling-up of the developing liquid is prolonged with simultaneous increase in the flow rate of the developing liquid in the rotational direction of the drum and decrease in the relative flow rate thereof with respect to the latent image surface, whereby the toner image is not affected by the liquid flow. It is also possible that a balance in the state of the liquid Welling-up is adjusted by changing the interval between the adjacent liquid feeding ports, the number and the diameter thereof as well as the angles a and B in conformity to the variations in the flowing quantity of the developing liquid into the electrode through the liquid feeding tube 14 depending on the capability of the pump.

FIG. 7 shows still another embodiment of the present invention, in which the slit-opening of the well-up groove 8b is directed to the lateral side along the rotational direction of the drum so as to further reduce the influence caused to the formed image by the flowing speed of the developing liquid. In addition, the developing liquid flow path 8a and the liquid storing sump 15 are so constructed that both are integrally formed and separated by a partition leaving a small slit-opening for the developing liquid to communicate therebetween. Further, as seen from the drawing, the developing liquid flow path 8a and the liquid storing sump 15 are disposed in an up-and-down relationship to secure the effects of the liquid stagnation in the sump l5 and the liquid Welling into the flow path 8a.

FIG. 8 shows further embodiment of the present invention, in which a plurality of the liquid storing sumps 15a and 15b are disposed in the vertical direction to further improve the control of the liquid flow rate, and at the same time, to secure satisfactory developing result even with the liquid feeding at a high speed in a large quantity, since the liquid speed becomes extremely slow at the well-up groove 8a.

In particular, as the liquid storing section can be parted by partition boards or walls, the manufacturing of the device is remarkably facilitated.

As has been described prescisely in the foregoing, the developing device according to the present invention is constructed in such a way that the developing liquid storing sump is provided prior to the liquid well-up groove so as to regulate the flow rate of the developing liquid and to enable the development of the image to be carried out satisfactorily at the development section.

Accordingly, the developing device according to the present invention, from which the influence on the formed image due to the flow rate of the developing liquid has been eliminated, can be constructed in an extremely compact dimension even in the case of the devclopment of a large surface area, hence its practical merit is very remarkable.

While the present invention has been illustrated and described by way of preferred embodiments thereof, it is to be understood that such are merely illustrative and not restrictive, and that variations and modifications may be made therein without departing from the spirit and scope of the present invention as recited in the appended claims.

We claim:

1. A developing device for developing, with a liquid developing agent, an electrostatic image formed on an image bearing member, comprising:

an electrode for development;

a reservoir for the developing agent;

slit well-up means for welling up the developing agent, said means being formed on said electrode and having closed ends;

means for controlling the flow of the developing agent, said controlling means being located adjacent said slit well-up means and including a storing sump for the liquid developing agent and a plurality of openings communicating the storing sump with said slit well-up means, the openings directing the liquid developing agent from the storing sump in a direction different from the wellup direction of the liquid developing agent at the slit of said well-up means; and

means for feeding the liquid developing agent from said reservoir to said controlling means.

2. A developing device for developing, with a liquid developing agent, an electrostatic image form on an image bearing member, comprising:

an electrode for development located at a lower position of a photosensitive drum, said electrode having an arcuate surface adapted for a surface of the photosensitive drum;

a reservoir for the developing agent;

well-up means for welling up the developing agent,

said means having closed ends and being formed on said electrode at a position thereof where the photosensitive drum rotates in the downward direction,

means for controlling the flow of the developing agent, said controlling means being located laterally adjacent said well-up means and including a storing sump for the liquid developing agent located a distance from said well-up means in a radial direction of the photosensitive drum, and alos including a plurality of openings communicating the storing sump with said well-up means; and

means for feeding the liquid developing agent from said reservoir to said controlling means.

3. A device according to claim 2, wherein the well-up direction of the liquid developing agent at said well-up means is eccentric with respect to the center of the photosensitive drum in the direction of rotation of the drum.

4. An electrophotographic apparatus comprising means for forming an electrostatic latent image on a photosensitive drum, means for developing the electrostatic latent image thus formed, means or removing excessive developing liquid from the photosensitive drum, means for transferring an image thus developed onto a transfer material, and means for cleaning the photosensitive drum, said means being located around the photosensitive drum in the order named, and said developing means being located lower than the level of the center of the photosensitive drum, and said developing means comprising,

an electrode having an arcuate surface adapted for a surface of the photosensitive drum,

a slit formed in the electrode to well up the developing liquid at a position where the photosensitive member rotates downwardly,

a developing liquid storing sump located in parallel with said slit, and

numerous openings for discharging the developing liquid from the storing sump in a substantially hori- 

1. A DEVELOPING DEVICE FOR DEVELOPING, WITH A LIQUID DEVELOPING AGENT, AN ELECTROSTTATIC IMAGE FORMED ON AN IMAGE BEARING MEMBER, COMPRISING: AN ELECTRODE FOR DEVELOPMENT, A RESERVOIR FOR THE DEVELOPING AGENT, SLIT WELL-UP MEANS FOR WELLING UP THE DEVELOPING AGENT, SAID MEANS BEING FORMED ON SAID ELECTRODE AND HAVING CLOSED ENDS, MEANS FOR CONTROLLING THE FLOW OF THE DEVELOPING AGENT, SAID CONTROLLING MEANS BEING LOCATED ADJACENT SAIDD SLIT WELL-UP MEANS AND INCLUDING A STORING SUMP FOR THE LIQUID DEVELOPING AGENT AND A PLURALITY OF OPENINGS COMMUNICATING THE STORING SUMP WITH SAID SLIT WELL-UP MEANS, THE OPENINGS DIRECTING THE LIQUID DEVELOPING AGENT FROM THE STORING SUMP IN A DIRECTION DIFFERENT FROM THE WELL-UP DIRECTION OF THE LIQUID DEVELOPING AGENT AT THE SLIT OF SAID WELL-UP MEANS, AND MEANS FOR FEEDING TH LIQUID DEVELOPING AGENT FROM SAID RESERVOIR TO SAID CONTROLLING MEANS.
 2. A developing device for developing, with a liquid developing agent, an electrostatic image form on an image bearing member, comprising: an electrode for development located at a lower position of a photosensitive drum, said electrode having an arcuate surface adapted for a surface of the photosensitive drum; a reservoir for the developing agent; well-up means for welling up the developing agent, said means having closed ends and being formed on said electrode at a position thereof where the photosensitive drum rotates in the downward direction, means for controlling the flow of the developing agent, said controlling means being located laterally adjacent said well-up means and including a storing sump for the liquid developing agent located a distance from said well-up means in a radial direction of the photosensitive drum, and alos including a plurality of openings communicating the storing sump with said well-up means; and means for feeding the liquid developing agent from said reservoir to said controlling means.
 3. A device according to claim 2, wherein the well-up direction of the liquid developing agent at said well-up means is eccentric with respect to the center of the photosensitive drum in the direction of rotation of the drum.
 4. An electrophotographic apparatus comprising means for forming an electrostatic latent image on a photosensitive drum, means for developing the electrostatic latent image thus formed, means or removing excessive developing liquid from the photosensitive drum, means for transferring an image thus developed onto a transfer material, and means for cleaning the photosensitive drum, said means being located around the photosensitive drum in the order named, and said developing means being located lower than the level of the center of the photosensitive drum, and said developing means comprising, an electrode having an arcuate surface adapted for a surface of the photosensitive drum, a slit formed in the electrode to well up the developing liquid at a position where the photosensitive member rotates downwardly, a developing liquid storing sump located in parallel with said slit, and numerous openings for discharging the developing liquid from the storing sump in a substantially horizontal direction. 